He is married to comics writer Louise Simonson (née Alexander, née Jones), with whom he collaborated on X-Factor from 1988 to 1989, and with whom he made a cameo appearance in the 2011 Thor feature film.

Simonson studied geology at Amherst College, with the intent of becoming an expert on dinosaurs.[2] In 1964 or 1965, Simonson discovered Marvel Comics, in particular that company's version of Thor, a title he read for four years.[1][2] From this he realized that drawing comics was more fun, and more feasible as a career than working outdoors in hot weather as a geologist or paleontologist, despite harboring a love for the latter that continued the rest of his life.[2][3][4] Simonson came to be heavily influenced by the artists who worked for Marvel, such as Jack Kirby, Steve Ditko, and Gil Kane, as well as British artist Jim Holdaway and European artists such as Moebius, Jean-Claude Mézières, Antonio Hernandez Palacios and Sergio Toppi.[2]

After graduating from Amherst with a degree in Geology,[2] Simonson took a year off, and then enrolled as an art major at the Rhode Island School of Design, graduating in 1972. His thesis project there was the 50-page black and white book The Star Slammers, which took him two years to write, pencil, letter and ink himself, and was published a sort of ashcan promotional comic book for the 1974 World Science Fiction Convention in Washington, D.C. (DisCon II). Simonson would later revisit Star Slammers throughout his career, publishing it through various publishers over the decades.[1][2]

In August 1972, Simonson traveled to New York with his Star Slammers portfolio, and met with Gerry Boudreau, a friend who worked for DC Comics, where, as Simonson recalls, many young artists had begun working in the 1970s, in contrast to Marvel, which Simonson perceived as more stagnant. Boudreau arranged a meeting between Simonson and editor Archie Goodwin. After meeting with Goodwin, Simonson went to DC's coffee room, where he saw Howard Chaykin, Michael Kaluta, Berni Wrightson and Alan Weiss sitting together. Simonson struck up a conversation with the artists, who looked at his portfolio. Kaluta showed Simonson's work to Assistant Production Manager Jack Adler, who in turn showed it to DC Publisher Carmine Infantino, who after being shown the portfolio, summoned Simonson into his office. After speaking to Simonson for about ten minutes, he had Goodwin and his fellow editors Julius Schwartz and Joe Orlando give Simonson work. Simonson walked out of Infantino's office with jobs from each one of them.[1]

Simonson's first professional published comic book work was illustrating writer Len Wein's story "Cyrano's Army", which appeared in DC's Weird War Tales #10,[1][5] which was covered dated January 1973. He also did a number of illustrations for the Harry N. Abrams, Inc. edition of The Hobbit, and at least one unrelated print of a samurai warrior that was purchased by Harvard University's Fogg Museum, and included in its annual undergraduate-use loan program. Simonson's breakthrough illustration job was "Manhunter", a backup feature in DC's Detective Comics written by Goodwin, which cemented Simonson's professional reputation.[1][6][7] In a 2000 interview, Simonson recalled, "What 'Manhunter' did was to establish me professionally. Before 'Manhunter,' I was one more guy doing comics; after 'Manhunter,' people in the field knew who I was. It'd won a bunch of awards the year that it ran, and after that, I really had no trouble finding work."[8] Simonson then drew other DC series such as Metal Men and Hercules Unbound[9] and co-created Doctor Phosphorus with Steve Englehart.[10]Batman #300 (June 1978) featured a story by Simonson and writer David Vern Reed.[11][12] In 1979 Simonson and Goodwin collaborated on an adaptation of the movie Alien, published by Heavy Metal. It was on Alien that Simonson's long working relationship with letterer John Workman began. Workman has lettered most of Simonson's work since.[9]

In 1979 Simonson did writing and art on a book for the first time with his run on Marvel's licensed Battlestar Galactica series,[2] penciling 12 sporadic issues from issues #4 to 23 with writer Roger McKenzie. Simonson began co-writing the series with McKenzie with issue #11, co-wrote some issues with Bob Layton and Steven Grant after McKenzie left the title, wrote began writing the book himself with issue #19, staying on until issue #23.[9]

Interior page from The Mighty Thor #346, story and art by Walter Simonson (1984).

In 1982, Simonson and writer Chris Claremont produced The Uncanny X-Men and The New Teen Titansintercompany crossover between the top-selling Marvel and DC titles.[16][17] Simonson is best known for his work on Marvel Comics' Thor which he began writing and drawing with issue #337 (Nov. 1983).[18] Simonson took nearly complete control of Thor, during which he transformed Thor into a frog for three issues and introduced the supporting character Beta Ray Bill, an alien warrior who unexpectedly proved worthy to wield Thor's hammer, Mjolnir.[19][20] He started as writer and artist with issue #337 (Nov. 1983) and continued until #367 (May 1986). Sal Buscema became the artist on the title with #368 but Simonson continued to write the book until issue #382 (Aug. 1987).[9] Buscema described Simonson's stories as "very stimulating. It was a pleasure working on his plots, because they were a lot of fun to illustrate. He had a lot of great ideas, and he took Thor in a totally new direction."[21] In late 1986 he dropped several of his assignments, including Thor, remarking that "I had a very busy season over the past six to eight months, and I'd like to take some time off, to take time maybe to take stock and refuel a bit."[22] Simonson was to have drawn a Daredevil story written by Frank Miller but it was never completed and remains unpublished.[23] Simonson joined his wife Louise on the X-Factor series with issue #10. In #25, the creators gave the character the Angel blue skin and metal wings in a process which would lead to his being renamed as "Archangel". Their run on X-Factor included the story arcs "Mutant Massacre", "Fall of the Mutants," and "Inferno".[9]

In 1983, he returned to Star Slammers with another version of the story that Marvel published in Marvel Graphic Novel No. 6.[2]

Simonson became writer of the Fantastic Four with issue #334 (Dec. 1989), and three issues later began penciling and inking as well (#337). For issues #347-349, he collaborated with Arthur Adams, introducing the "New Fantastic Four" consisting of Wolverine, Spider-Man, Ghost Rider and the Hulk.[25][26][27] In issue #345 he depicted dinosaurs with feathers, two decades before this idea gained mainstream acceptance among paleontologists. Simonson's decision to depict the dinosaurs in this manner was inspired by Arthur Paul's then-controversial book, Predator Dinosaurs of the World, in which Paul theorized that dinosaurs had feathers. Because this idea was met with skepticism from the scientific community at the time, Simonson decided to compromise by depicting the dinosaurs with a small amount of feathers, rather than covered with them.[28] Simonson left the Fantastic Four with issue #354 (July 1991). His other Marvel credits in the decade included co-plotting/writing the Iron Man 2020 one-shot (June 1994) and writing the Heroes Reborn version of the Avengers.[9]

In 1994 Simonson continued the adventures of the Star Slammers in a limited series as one of the founders of Malibu Comics' short-lived Bravura label.[2]

Other work in the 2010s includes drawing six issues of The Avengers vol. 4 in 2012 and providing the artwork for three issues of The Indestructible Hulk which guest starred Thor. Simonson collaborated with his wife for a short story in Rocketeer Adventures vol. 2 #4 and drew covers for several Rocketeer comics during this period.[9]

In 2012 DC Comics published The Judas Coin,[9] a graphic novel written and drawn by Simonson. The book shows how one silver coin paid to Judas to betray Jesus affects various characters down the centuries including Batman.

Simonson's creator-owned series Ragnarök published by IDW Publishing features a version of Thor unrelated to the Marvel character. The first issue was published in July 2014.[34]

Simonson's awards include Shazam Awards for Outstanding New Talent in 1973, for Best Individual Short Story (Dramatic) in 1973 for "The Himalayan Incident" in Detective Comics #437 (with Archie Goodwin), and the same award in 1974 for "Cathedral Perilous" in Detective Comics #441 (again with Archie Goodwin). Simonson and Goodwin also won the Shazam Award for Best Individual Story (Dramatic) in 1974 for "Götterdämmerung" in Detective Comics #443. All three winning stories were a part of the Manhunter saga.

A collection of Simonson's Thor comics shot from the original art, published as part of IDW's Artist's Edition series, took the 2012 Eisner Award for "Best Archival Collection/Project: Comic Books"[38] and two Harvey Awards for "Best Domestic Reprint Project and a Special Award for Excellence in Presentation".[39]

Simonson's distinctive signature consists of his last name, distorted to resemble a Brontosaurus. Simonson's reason for this was explained in a 2006 interview. "My mom suggested a dinosaur since I was a big dinosaur fan."[40][41]

Simonson inked his own work with a Hunt 102 Pro-quill pen. He switched to a brush during the mid-to-late 2000s, and despite the disparity between the two tools, Bryan Hitch, an admirer of Simonson's, stated that he could not tell the difference, calling Simonons's brush work "as typically good and powerful as his other work."[42]

^Trumbull, John (December 2013). "A New Beginning...And a Probable End Batman #300 and #400". Back Issue!. Raleigh, North Carolina: TwoMorrows Publishing (69): 49–53.

^Manning "1970s" in Dougall, p. 128: "Crafted by writer David V. Reed and penciller Walter Simonson, this special 34-page issue imagined a possible future where Gotham City had become the hub of Magalopolis-East."

^Sanderson, Peter; Gilbert, Laura, ed. (2008). "1970s". Marvel Chronicle A Year by Year History. London, United Kingdom: Dorling Kindersley. p. 178. ISBN978-0756641238. In these stories, written by Doug Moench and drawn by Walter Simonson, the Hulk contended against an invading race of aliens called the Krylorians.

^Manning, Matthew K. "1980s" in Dolan, p. 199: "The issue, written by longtime X-Men scribe Chris Claremont and drawn by Walter Simonson [was]...one of the most well-received crossovers of its time - or of any time for that matter - the team-up was a huge success."

^Brown, Jonathan (August 2013). "The Uncanny X-Men and The New Teen Titans: The Breakfast Club of the Comics Crossover". Back Issue!. Raleigh, North Carolina: TwoMorrows Publishing (66): 65–68.

^DeFalco, Tom "1980s" in Gilbert (2008), p. 213: "This issue began a highly acclaimed run by writer/artist Walt Simonson that would last for nearly four years and end with issue #382 (Aug. 1987)."

^Mithra, Kuljit (August 1997). "Interview With Walt Simonson". ManWithoutFear.com. Archived from the original on March 13, 2013. Retrieved March 17, 2013. The gist of it is that by the time Marvel was interested in having us work on the story, Frank was off doing Dark Knight and I was off doing X-Factor. So it never happened. Too bad--it was a cool story too.

^Manning, Matthew K. "1990s" in Gilbert (2008), p. 252: "Spider-Man, the Hulk, Wolverine, and Ghost Rider were tricked into forming a new Fantastic Four...Written by Walter Simonson with art by Arthur Adams, this new FF found themselves locked in battle with the Mole Man."

^Cowsill, Alan; Gilbert, Laura, ed. (2012). "1990s". Spider-Man Chronicle Celebrating 50 Years of Web-Slinging. London, United Kingdom: Dorling Kindersley. p. 186. ISBN978-0756692360. Take Spidey, Ghost Rider, Wolverine, and the Hulk, add a script by Walt Simonson and illustrations by Art Adams, and the result is one of the best Marvel comics of the decade.

^Cronin, Brian (July 3, 2015). "Comic Book Legends Revealed #530". Comic Book Resources. Archived from the original on July 5, 2015. This is because Simonson...decided to be as accurate as he possibly could in the depiction of the dinosaurs in the issue. He relied heavily on Gregory Paul's book, Predator Dinosaurs of the World, which was a controversial call at the time as Paul’s theories regarding dinosaurs having feathers was not yet proven and drew much skepticism from other scientists.

^Cowsill, Alan "2000s" in Dolan, p. 296 "Comic book legend Walt Simonson brought his unique vision to one of Jack Kirby's greatest heroes on Orion, the first ongoing series to feature the most prominent of the New Gods."